Shadowbringers Bard essentially lost even the pretense of any above-average party support utility, along with generally making their rotation a fair bit more dull.
- Heavensward Bard: Sustained frequency of DoTs roughly halved compared to ARR due to the addition of Iron Jaws (though at least that makes maintenance more strict and often shortens their effective duration by 1 GCD, since you could previously let them drop after getting the server tick and reapply before the next server tick), but with a new rotational weaponskill per 6 GCDs (that functioned mostly half like an oGCD, since it incurred but did not respect the global cooldown), a sniper vs. mobile stance (decent concept, but very poorly iterated upon), and a couple other new CDs to play with. Support functions remain granular but at-cost (to raidbuff uptime, 10% personal DPS, and a GCD for swapping). Their filler's proc also became more valuable for the mobility it offers at no cost during sniper stance. I think it was here also that the LB3 was changed from Healer-LB3 to Caster-LB3-but-as-a-Line-Attack?
- Stormblood Bard: Support functions gutted insofar as their gameplay, becoming instead CDs that are basically hit on CD after their first use per fight going towards personal threat reduction. Stances removed. Frequency of DoT/buff GCDs reduced again (now at 2 per 12 GCDs, down from ARR's 3 per 7 GCDs). In place of songs offering support tools aside from the still-granular raid buff, they now create a new system of rotated stances that are freely ordered initially but cannot really be chosen between thereafter. Battle Voice changed from a versatile support-capable tool to a generic raid buff. Filler's proc replaced with a new action, such that one maintains their buff shot per 30s. ARR's original DoT interaction limited to a single song/rotary_buff, but the other two gain new DoT interactions. Lost job-synergy interactions with Warden's Paeon (namely with post-Berserk pacification), but did get access to Palisade as a wonky single-target mitigation buff.
- Shadowbringers Bard: Buffing GCD removed (iirc?), reducing sustained non-filler/procced_filler actions yet again by 50%. Even the vestigial support functions were removed. Granular raid buff removed, leaving only Battle Voice. Added Apex Arrow. Barrage now grants the new proc so it can't become desynced by more than a single GCD. Palisade removed.
- Endwalker Bard: Non-filler/procced_filler actions reduced yet again (from 1 per 12 to 1 per 18). All DoT interactions removed. Apex Arrow gets a part-2. Radiant Finale added, which can at least (poorly) pretend not to be a simple 120s raid buff.
Red Mage didn't particularly get hit with any new gameplay issues, iirc. He was just saying it's what he swapped to because of Bard, in his opinion, becoming less appealing due to its ShB changes.